Conventional spool hub systems for welding machines include a braking system which prevents the spool of wire from overspooling inside the welding machine. These systems vary from electronic brakes to simple brake washers with a spring force applied to the brake washer.
Conventional welding machines which use spring-based brake washers have a nut which is threaded onto an end of a threaded spool hub shaft. An example of such a conventional welding machine 10 is shown in FIGS. 1 and 2. The spring 12 is between the nut 14 and a spool hub 16 mounted on the spool hub shaft 18. The nut 14 is tightened on the spool hub shaft 18 to adjust the pressure of the spring 12 on the spool hub 16 which, in turn, adjusts the pressure of the spool hub 16 bearing against the brake washer 20. Sometimes, the nut 14 appears to be loose to the user, and upon seeing this, the user may tighten the nut 14 to what they “feel” is the correct amount of torque, since the threaded connection between the nut 14 and the spool hub 16 allows an infinite range of torque adjustment (subject to the length of the thread). Sometimes, this new torque is too tight and prevents the spool hub 16 from spinning on the spool hub shaft 18 as the spool hub 16 is bound too tightly between the spring 12 and the brake washer 20. Also sometimes, the user does not apply sufficient tension, which could allow the wire spool 22 to overspool.